Portable computing using light-weight mobile data processors has become more pervasive as mobile data processors become more computationally powerful. However, with conventional practice use of the portable computer outside of an office or similar environment requires decoupling the portable computer from a network. This is due to current requirements for maintaining a wired connection when using computer networks.
Wireless communication between two points is well known and is typically accomplished using radio frequency (RF) communication techniques. An alternative for an indoor environment, such as an office building, is through the use of infrared (IR) radiation as a communication medium.
In IBM Technical Disclosure Bulletin Vol. 24 No. 8, 1982 F. Gfeller describes general control principles of an infrared wireless communication network incorporating multiple base stations and multiple mobile computers. Transmission occurs over the wireless IR medium using different frequencies for the uplink and the downlink but a single wavelength. This article does not discuss the issue of collision detection.
In U.S. Pat. No. 4,807,222, issued Feb. 21, 1989, N. Amitay discloses a wireless network using intelligent interfaces for each wired network connection. The interface is to a token bus network, not to a CSMA/CD network, thereby requiring that the wired and wireless networks be asynchronous from one another.
In U.S. Pat. No. 4,665,519, issued May 12, 1987, T. L. Kirchner et al., disclose a specific application using VHF FM radio as a means of connecting computers and computer peripherals. This patent describes in detail the implementation of an asynchronous access, token based protocol and does not address the issue of collision detection. Furthermore, the protocol appears to support only relatively low data rate communication and requires microprocessor control for each interface.
In International Patent WO88/07794, published Oct. 6, 1988, G. Vacon discloses the use of a wireless microwave bridge between two networks utilizing the CSMA/CD protocol. Vacon however does not consider a network interface for mobile computers to a CSMA/CD local area network. The interface is required to store messages before forwarding them to their destination and also does not address the problem of providing CSMA/CD on a wireless network involving many wireless devices. Collision detection occurs on the wired network but not on the wireless network.
One problem with the techniques presented by this prior art is that there is not provided a wireless network that is low in cost and that provides asynchronous multiple access with collision detection on the wireless network itself. The patents all operate with some variant of a "store and forward" mechanism, which adds complexity and cost to the overall system. The patents also consider networks employing synchronous access, peer to peer only, or asynchronous wired and wireless networks; and not a system wherein access is asynchronous for many users while also being synchronous with the wired network.
It is thus an object of the invention to provide for coupling a wireless communication network to a wired network that employs a CSMA/CD protocol.
It is a further object of the invention to provide a wireless network that utilizes separate wavelengths for an uplink and a downlink channel to facilitate the provision of collision detection on the wireless network.
It is a still further object of the invention to provide for a low complexity and low cost transceiver, and a method of operating same, for transparently coupling nodes of a wireless network to a standard, as opposed to a proprietary, local area wired network.